Fracture identification is important for the evaluation of carbonate reservoirs. However, conventional logging equipment has small depth of investigation and cannot detect rock fractures more than three meters away fr...Fracture identification is important for the evaluation of carbonate reservoirs. However, conventional logging equipment has small depth of investigation and cannot detect rock fractures more than three meters away from the borehole. Remote acoustic logging uses phase-controlled array-transmitting and long sound probes that increase the depth of investigation. The interpretation of logging data with respect to fractures is typically guided by practical experience rather than theory and is often ambiguous. We use remote acoustic reflection logging data and high-order finite-difference approximations in the forward modeling and prestack reverse-time migration to image fractures. First, we perform forward modeling of the fracture responses as a function of the fracture-borehole wall distance, aperture, and dip angle. Second, we extract the energy intensity within the imaging area to determine whether the fracture can be identified as the formation velocity is varied. Finally, we evaluate the effect of the fracture-borehole distance, fracture aperture, and dip angle on fracture identification.展开更多
To test the accuracy of real-time three-dimensional echocardiography (RT3DE) imaging system for evaluating left ventricular mass (LVM) in phantom and excised canine heart. Methods Ten left ventricular (LV) wall phanto...To test the accuracy of real-time three-dimensional echocardiography (RT3DE) imaging system for evaluating left ventricular mass (LVM) in phantom and excised canine heart. Methods Ten left ventricular (LV) wall phantoms made of two rubber-bursas, ten excised canine hearts underwent RT3DE and two-dimensional echocardiography (2DE). In RT3DE "full volume" imaging, the myocardial volume was mea-sured using 2,4,8, and 16-plane method with the analysis software of RT3DE. Mass was then calculated by multiplying the resulting myocardial volume by specific density of myocardial tissue. In 2DE the masses were measured by area-length meth-od. The true LV wall phantom mass was measured by water displacement and the canine LVM was weighed by anatomy, which served as a reference standard. We compared RT3DE or 2DE with true mass. Results In LV wall phantoms, RT3DE correlated with true masses strongly (r = 0.813-0.994) and weakly correlated between 2DE and true masses (r = 0.628). In excised canine hearts, there is an excellent correlation between RT3DE and true masses (r = 0.764-0.991), while 2DE value showed a lesser correlation (r = 0.514). There are no difference between RT-3DE and true masses (P > 0.05) but different between 2DE and true masses (P < 0.05). In different planes, there was no difference between 8-plane and 16-plane (P > 0.05) but different between 8-plane and 2, 4-plane (P < 0.05). Conclusion RT3DE can accurately quantify LVM and provide a new tool to evaluate LV function. For LVM by RT3DE, 8-plane measurement method is the best choice for accuracy and convenience.展开更多
In this paper we study the mean first passage time （MFPT） over a fluctuation potential barrier driven by a coupled noise. It is shown that the MFPT over the fluctuation potential barrier displays resonant activation...In this paper we study the mean first passage time （MFPT） over a fluctuation potential barrier driven by a coupled noise. It is shown that the MFPT over the fluctuation potential barrier displays resonant activations as the function of the flipping rate of the fluctuation potential barrier, and as the function of the dichotomous noise transition rate.展开更多
We present an experimental study on the motion of a spherical droplet in a plane traveling sound wave.The experiments were performed in the test section of a tunnel with two loudspeakers at the two ends of the tunnel....We present an experimental study on the motion of a spherical droplet in a plane traveling sound wave.The experiments were performed in the test section of a tunnel with two loudspeakers at the two ends of the tunnel.By adjusting the amplitude ratio and the phase difference between the two speakers,a plane traveling sound wave field can be achieved in the test section of the tunnel,which we checked by measuring the amplitudes and phases of the sound pressure along the tunnel and by simultaneously measuring the velocity field of the air flow at three different locations in the tunnel.When a liquid droplet was introduced in the test section,the motion of the droplet and the velocity of the air flow around the droplet were recorded by high speed cameras,from which we analyze and obtain the ratio of the velocity amplitudes and the phase difference between the particle motion and the fluid motion.The experimental data confirm the theoretical result from the wave equations in the long-wavelength regime,i.e.,when the particle size is much smaller than the wavelength.Moreover,we showed that in this regime,the theory on particle motion in an unsteady uniform fluid,when the history term is included,also yields the same results that are in agreement with the experimental data and the wave equation.Our result extends the parameter range over which the theory on particle motion in unsteady fluid is checked against experiments,especially to the range of particle-fluid density ratio that is of important practical applications.展开更多
基金supported by National Petroleum Major Project(Grant No.2011ZX05020-008)
文摘Fracture identification is important for the evaluation of carbonate reservoirs. However, conventional logging equipment has small depth of investigation and cannot detect rock fractures more than three meters away from the borehole. Remote acoustic logging uses phase-controlled array-transmitting and long sound probes that increase the depth of investigation. The interpretation of logging data with respect to fractures is typically guided by practical experience rather than theory and is often ambiguous. We use remote acoustic reflection logging data and high-order finite-difference approximations in the forward modeling and prestack reverse-time migration to image fractures. First, we perform forward modeling of the fracture responses as a function of the fracture-borehole wall distance, aperture, and dip angle. Second, we extract the energy intensity within the imaging area to determine whether the fracture can be identified as the formation velocity is varied. Finally, we evaluate the effect of the fracture-borehole distance, fracture aperture, and dip angle on fracture identification.
文摘To test the accuracy of real-time three-dimensional echocardiography (RT3DE) imaging system for evaluating left ventricular mass (LVM) in phantom and excised canine heart. Methods Ten left ventricular (LV) wall phantoms made of two rubber-bursas, ten excised canine hearts underwent RT3DE and two-dimensional echocardiography (2DE). In RT3DE "full volume" imaging, the myocardial volume was mea-sured using 2,4,8, and 16-plane method with the analysis software of RT3DE. Mass was then calculated by multiplying the resulting myocardial volume by specific density of myocardial tissue. In 2DE the masses were measured by area-length meth-od. The true LV wall phantom mass was measured by water displacement and the canine LVM was weighed by anatomy, which served as a reference standard. We compared RT3DE or 2DE with true mass. Results In LV wall phantoms, RT3DE correlated with true masses strongly (r = 0.813-0.994) and weakly correlated between 2DE and true masses (r = 0.628). In excised canine hearts, there is an excellent correlation between RT3DE and true masses (r = 0.764-0.991), while 2DE value showed a lesser correlation (r = 0.514). There are no difference between RT-3DE and true masses (P > 0.05) but different between 2DE and true masses (P < 0.05). In different planes, there was no difference between 8-plane and 16-plane (P > 0.05) but different between 8-plane and 2, 4-plane (P < 0.05). Conclusion RT3DE can accurately quantify LVM and provide a new tool to evaluate LV function. For LVM by RT3DE, 8-plane measurement method is the best choice for accuracy and convenience.
基金The project supported by National Natural Science Foundation of China under Grant No. 10375009, and the Scientific Research Foundation for the Returned 0verseas Chinese Scholars, State Education Ministry and by K.C. Wong Magna Fund in Ningbo University
文摘In this paper we study the mean first passage time （MFPT） over a fluctuation potential barrier driven by a coupled noise. It is shown that the MFPT over the fluctuation potential barrier displays resonant activations as the function of the flipping rate of the fluctuation potential barrier, and as the function of the dichotomous noise transition rate.
基金This work was supported partially by the National Natural Science Foundation of China(Grant No.11988102)and by Tsinghua University.
文摘We present an experimental study on the motion of a spherical droplet in a plane traveling sound wave.The experiments were performed in the test section of a tunnel with two loudspeakers at the two ends of the tunnel.By adjusting the amplitude ratio and the phase difference between the two speakers,a plane traveling sound wave field can be achieved in the test section of the tunnel,which we checked by measuring the amplitudes and phases of the sound pressure along the tunnel and by simultaneously measuring the velocity field of the air flow at three different locations in the tunnel.When a liquid droplet was introduced in the test section,the motion of the droplet and the velocity of the air flow around the droplet were recorded by high speed cameras,from which we analyze and obtain the ratio of the velocity amplitudes and the phase difference between the particle motion and the fluid motion.The experimental data confirm the theoretical result from the wave equations in the long-wavelength regime,i.e.,when the particle size is much smaller than the wavelength.Moreover,we showed that in this regime,the theory on particle motion in an unsteady uniform fluid,when the history term is included,also yields the same results that are in agreement with the experimental data and the wave equation.Our result extends the parameter range over which the theory on particle motion in unsteady fluid is checked against experiments,especially to the range of particle-fluid density ratio that is of important practical applications.
